Human immunodeficiency virus infection/acquired immunodeficiency syndrome (HIV/AIDS) is a disease of the human immune system caused by the infection with human immunodeficiency virus (HIV). Since its discovery in the early 1980s, AIDS has become a pandemic and caused more than 25 million deaths. Approximately 35 million people are currently living with HIV/AIDS globally, urgently in need of effective, affordable, long-term treatment and management of the disease.
HIV can infect a variety of immune cells, with CD4+ T cells and monocytes/macrophages being the major targets. HIV attacks a target cell first by fusion of the viral envelope with the cell membrane and release of the HIV capsid into the cell. Inside the infected cell, the single-stranded RNA genome of the HIV is reverse transcribed into a double-stranded viral DNA, and the viral DNA is integrated into the infected cell's genome. Then cellular machineries of the infected cell are hijacked to produce the RNA genome as well as the protein components of the virus, which assemble into immature HIV virions inside the infected cell. After the final assembly at the cell surface, the immature HIV-virions bud from the cell membrane of the infected cell and after the final step of protease cleavage, the resultant mature virions are released, completing a replication cycle. HIV rapidly replicates in the first 2-4 weeks after infection, leading to a marked drop in the number of circulating CD4+ T cells. Upon mobilization of the still largely intact immune system to fight HIV replication, the virus level is controlled and the CD4+ T cell counts stabilize such that the HIV infection enters clinical latency, and the latency can last from about three years to over 20 years. As the HIV erodes the immune system, eventually the level of CD4+ T cells drops to an alarming level and HIV infection progresses into AIDS. AIDS patients often die of opportunistic infections as a result of the collapse of their immune systems. HIV may also damage the nervous system, entering the brain through infected immune cells early on in the infection and further spreading to the central nervous system (CNS)-resident immune cells, such as microglia and astrocytes. These infections may damage the brain and spinal cord and cause symptoms such as confusion and forgetfulness, behavioral changes, headaches, progressive weakness, and loss of sensation in the arms and legs.
The mainstream treatment of AIV/AIDS is the highly active antiretroviral therapy (HAART), which uses combinations (or “cocktails”) of compounds that include multiple classes of antiviral agents. Virus production in infected individuals is largely the result of a dynamic process involving continuous rounds of de novo infection of and replication in activated CD4+ T cells with rapid turnover of both free virus and virus-producing cells. These antiviral cocktails inhibit steps of HIV's replication cycle, including entry, reverse transcription, integration, assembly and release. HAART therefore suspends the HIV replication cycle, causing depletion of the immature HIV virions and the host cells, resulting in containment of HIV infection.
Current antiviral therapy, however, does not eradicate HIV infection, because other HIV-infected cells, including the resting memory CD4+ T cells and the monocytes/macrophages, have long half-lives and therefore serve as virus reservoirs. HAART also suffers the drawbacks of high cost, adverse toxic effects, drug interactions, and drug resistance. These adverse effects sometimes make it necessary to introduce structured therapy interruptions (“TI”, or drug holidays) or cease the treatment altogether. Drug resistance is a significant problem in HAART: the reverse transcription of HIV RNA is prone to mistakes, resulting in introduction of mutations into the viral genome. Continued antiviral drug administration provides natural selection for drug-resistant mutant virus strains. There is a theory that TI may allow more “fit” wild-type drug-susceptible viruses to outgrow the less “fit” drug-resistant mutant strains. For this additional reason, it is often recommended to interrupt the antiviral therapy in a structured manner. However, rebound of plasma viral loads (VL) and decline in CD4+ T cell counts is common during TI, thereby negating the effect of the HAART treatment. Virions, in particular drug-resistant virions, sequestered in HIV reservoirs are no longer suppressed during TI and may mature and be released. This is thought to be the cause of therapy setback during TI and the less effective suppression frequently afforded by HAART when subsequently reintroduced.
Infected resting memory CD4+ T cells, monocytes and macrophages are reservoirs for HIV, including the drug-resistant strains. In addition, monocytes produce cytokines, e.g., TNFα, that induce HIV replication in other infected cells, e.g., CD4+ T cells. Infected activated macrophages are able to trigger apoptosis of uninfected T cells and protect HIV-infected T cells from apoptosis. Monocytes and macrophages therefore provide a pool of viruses ready to replicate during TI, and their physiological activity further amplifies the damage of HIV infection to the immune system. A few studies have targeted monocytes and macrophages as a treatment of HIV/AIDS, however, the therapeutic efficacy of these approaches has been limited.
Clinical studies testing the effect of purging circulating monocytes by selective apheresis produced mixed results. Selective apheresis involves passing the blood of HIV-infected, HAART-receiving patients through an extracorporeal apparatus to remove circulating monocytes and granulocytes. In one study, apheresis during HAART treatment did not affect plasma HIV-1 RNA load compared to controls, but reduced TNFα level and increased CD4+ T cell counts after 3-4 apheresis sessions. (Beretta, A. et al., J. Biol. Regulators and Homeostatic Agents 14, 27-31 (2000).) In another study, selective apheresis of monocytes and granulocytes was conducted during the first 5 weeks of TI. Upon reintroduction of HAART, the apheresis group exhibited an increase in CD4+ T cell counts. HAART reintroduction failed to suppress viral rebound in most, but not all, of the control group, whereas, the most of the apheresis group exhibited virologic suppression. A reduction of monocyte HIV viral load of up to 52% was observed in some of the apheresis group, but enhancement comparable to controls was observed in others. (Hasson, H. et al., J. Med. Virol. 79, 1640-49 (2007).) These limited results might be accounted for by the fact that apheresis results in an average reduction of only 30% of circulating monocytes, and circulating monocytes represent a small fraction of the total body monocyte/macrophage pool. Another limitation of such approaches is that apheresis is an invasive and time-consuming in-patient procedure, which can significantly burden patients.
Other researchers also tested macrophage-inhibiting drugs in HIV animal models and saw positive effects on viral load control and CD4+ T cell rebound after HAART cessation. To achieve the specific and effective targeting of macrophages, the drugs were loaded in erythrocyte ghosts (erupted red blood cells). (see Cervasi, B. et al., J. Viol. 80, 10335-45 (2006); Serafini, S. et al., Antirivial Res. 81, 93-102 (2009).) Erythrocyte ghosts are difficult to prepare and store, however, making them a less than ideal choice for delivering drugs in great demand. Additionally, erythrocyte ghosts release their contents rapidly because of inherent leakage and the normal physiological process that eliminates red blood cells. The resultant elevated plasma drug concentration leads to toxicological problems. (See Lanao, J. M. et al., J. Drug Targeting 15(1), 21-36 (2007).)
Because a reliable cure or effective HIV vaccine still evades scientists, it is vital to slow the progression of HIV infection and maintain clinical latency as long as possible. Accordingly, there is a need in the art for a safe and effective approach to suppress virus replication in HIV/AIDS patients to complement HAART, in particular during TI. In addition, it is desirable that such approach is easy to administer and has the potential for mass production to meet the demand of a large HIV/AIDS population.
The current invention provides the advantage of specifically targeting monocytes and macrophages, the HIV latent reservoirs, preventing or delaying the rebound of HIV viral loads. The formula is expected to improve TI safety and extend the length of TI. Considering the physical and financial burden of HAART on HIV/AIDS patients and the public health system, safer and longer TI is highly desirable for the long-term management of the disease. Compared to the prior art, as adjunct therapy to HIV/AIDS antiviral treatment, the formulation of the invention is easy to administer, non-invasive, easy to store and distribute, and adaptable for mass production.